The invention relates to a novel anode coating used on anodes in electrolytic cells and more particularly in cells for the electrolysis of alkali halides.
For some 20 years electrodes made from metals such as titanium and tantalum have been proposed and titanium anodes are, in fact, progressively replacing graphite electrodes in commercial sodium chloride electrolysis operations. These electrodes have a coating of precious metals such as platinum, iridium, ruthenium, etc., whose consumption during electrolysis, although low by weight, is not economically negligible due to the high price of these precious metals. A great deal of research has been carried out with the aim of substituting less noble metals for these very expensive metals, but none of the hitherto proposed solutions has led to industrial development, thereby demonstrating that they have not been very satisfactory. In particular, patent literature exists relating to perovskite coatings connected to the substrate by cobalt oxide, but the coating is still relatively expensive.
An anode coating has now been discovered which does not cause a significant over-voltage during electrolysis of an alkali halide and which has proved to be remarkably stable on contact with the electrolyte and the chlorine given off during electrolysis.
It is, therefore, an object of the present invention to provide a novel coating of anodes for use in electrolysis.
It is another object of the invention to provide novel anode coatings which have superior stability and do not cause significant over-voltage during electrolysis of alkali halides.
Other objects of the invention will be apparent to those skilled in the art from the present disclosure.